This study is designed to analyze the cellular immunologic response made by the spleen, thymus, lymph node, and macrophage compartments that protects C58 mice from syngeneic line Ib lymphatic leukemia. Cell subpopulations in the immune response also will be analyzed. The effects of X-ray and drugs on the immune response also will be determined. The effects of adjuvants on the immune response also will be determined. The tumor antigen associated with line Ib syngeneic malignant lymphocytes will be isolated and characterized. BIBLIOGRAPHIC REFERENCES: Lukasewycz, O.A., Duffey, P.S., and W. H. Murphy. 1976. Immune Mechanisms in Leukemia: Protective Capacity of the Major Lymphoid Cell Compartment. J. Immunol. 116:976-981. Martinez, D., Lukasewycz, O.A., and W.H. Murphy. 1975. Immune Mechanisms in Leukemia: Suppression of Cellular Immunity by Drugs and X-irradiation. J. Immunol. 115:724-729.